1. Ambiphilic Metal-Ligand Assisted (AMLA) C-H Activation

We have developed the concept ofAmbiphilic Metal-Ligand Assisted(AMLA) C-H activation. In this process an agostic interaction to an unsaturated metal centre combines with H-bonding to a basic co-ligand to facilitate C-H bond cleavage. With aromatic C-H activation at [Pd(OAc)2] this mechanism supersedes the long-proposed Wheland-type intermediate. AMLA can account for facile C-H bond cleavage of both e--deficient and e--rich aromatic substrates at a range of late transition metal centres.

Figure 1.Computed agostic Intermediate in the AMLA-6 C-H Activation of dimethylbenzylamine at [Pd(OAc)2].

2. Metallophosphoranes and Aromatic C-F Bond Activation

We have defined novel ligand-assisted mechanisms for breaking the strong C-F bond of fluoroaromatics. This process involves nucleophilic attack by an e--rich metal centre with addition of a C-F bond over the M-L moiety, where L can be PR3, SiR3or BR2. For L= PR3metallophosphoranes, [LnM-(PFR3)], are formed as intermediates or transition states. Metallophosphoranes also play a role in the unusual M-F/P-R exchange reactions, such as the interconversion of [RhF(PPh3)3] to [Rh(Ph)(PFPh2)(PPh3)2].

3. Ruthenium N-Heterocyclic Carbene (NHC) Complexes in Catalysis

NHC ligands often confer enhanced reactivity on metal complexes. An example is the hydrodefluorination of C6F5H to give 1,2-C6F4H2catalysed by [Ru(H)2(CO)(NHC)(PR3)2] species. Calculations show this unusual ortho-selectivity arises from a nucleophilic attack mechanism where the hydride ligand (and not the metal) acts as the reacting species. Calculations also aim to understand the stability of NHC ligands towards metal-based decomposition reactions such as C-H, C-C and C-N activation.

Figure 3.Nucleophilic attack of a hydride ligand at the ortho position of C6F5H.